It is known that over 90% of Down's syndrome individuals develop Alzheimer-type dementias as they age. This aging Down's syndrome population is being studied audiologically in comparison to healthy normally aging males and females and in comparison to Alzheimer's patients. Each Down's syndrome patient receives complete audiologic assessments, including baseline and serial measurements of auditory function and electrophysiological studies. As of 1 May 1985, 25 adult Down's Syndrome patients (18 females; 17 males) have been evaluated audiologically. As this study is ongoing, some preliminary audiologic data was presented at a large meeting of speech and hearing professionals in November, 1984. Further analysis of the mixed hearing losses (over 80% of this population has some peripheral auditory deficit) will follow completion of data collection. Audiologic monitoring of this population is critical for professional and home management, as well as to maintain social and vocational development.